Displays in image display devices, such as television devices, are now being shifted from conventional cathode-ray tube displays to thin displays, such as liquid crystal displays and plasma displays. With the thin displays, thicknesses of the image display devices can be decreased. Liquid crystal panels do not emit light. Therefore, liquid crystal display devices including liquid crystal panels require backlight devices.
In the backlight devices, light sources mounted on light source boards generate heat on the light source boards while emitting light. Therefore, effective heat dissipation is required for the backlight devices to release the heat generated on the light source boards to the outside of the backlight devices. An example of edge-light type backlight devices in which heat generated on the light source boards can be effectively released to the outside is disclosed in Patent Document 1.